Support custom managers in Django models

For the moment this support is limited to just Model.objects
replacements and does not use the custom manager for ForeignKey
related managers.

test/completion/django.py

@@ -6,9 +6,18 @@ from django.db import models
 from django.contrib.auth.models import User
 
 
+class TagManager(models.Manager):
+    def specially_filtered_tags(self):
+        return self.all()
+
+
 class Tag(models.Model):
     tag_name = models.CharField()
 
+    objects = TagManager()
+
+    custom_objects = TagManager()
+
 
 class Category(models.Model):
     category_name = models.CharField()
@@ -155,6 +164,16 @@ model_instance.objects.update(x='')
 #? BusinessModel()
 model_instance.objects.create()
 
+# -----------------
+# Custom object manager
+# -----------------
+
+#? TagManager()
+Tag.objects
+
+#? TagManager()
+Tag.custom_objects
+
 # -----------------
 # Inheritance
 # -----------------